Sweetening agents are a class of food additives that have wide applications in the production of food products, beverages and candy. They may be added in the production process of a food product, or alternatively may be used through appropriate dilution as a surrogate for sucrose during household baking. Sweetening agents include natural sweetening agents, for example, sucrose, high fructose corn syrup, honey, etc., and artificial sweetening agents, for example, aspartame, saccharine, etc. Steviosides are a class of natural sweetening agents extracted from the plant Stevia rebaudiana, and are widely used in food products and beverages at present. The extract of Stevia rebaudiana contains a variety of steviosides comprising rebaudioside. Naturally extracted steviosides have great differences in ingredients across different batches, and need subsequent purification. A current commercialized product rebaudioside A comprises some other steviosides, for example, rebaudiosides C, D and F, etc. Stevioside prepared by an extraction method generally further has some impurities mixed therein, which will cause a certain influence on the application field thereof. Rebaudioside M has advantages over rebaudioside A, but has a very low content in leaves of Stevia rebaudiana, and is detected only in a Stevia rebaudiana Morita plant (2010, J. Appl. Glycosci., 57, 199-209). There is yet to be any commercialized production of rebaudioside M at present.